The long term goal of this work is to understand the entire regulatory program of IgH gene expression in B cells including early processes which activate transcription and target rearrangement, how growth and maturation signals are transduced to affect gene expression, the mechanism and factors which initiate transcription at different developmental stages, the nature of post-transcriptional regulatory mechanisms and how various regulatory networks interact. This knowledge will reveal general principles of tissue-specific and developmentally regulated gene expression, suggest molecular defects which may cause autoimmune and immune deficiency disease and identify unique regulatory features associated with gene rearrangement that may provide insight into other complex systems which generate information by combinatorial mechanisms. Based on our past work, there is a good understanding of the DNA sequences and cellular proteins which are important in IgH gene transcription. The current proposal is to clone cDNAs for transcription factors which bind to IgH promoter and enhancer sequences. Expression of cDNAs will provide chemical amounts of purified transcription factors for ; 1) structural and functional analyses of factor domains, ii) production of antibodies to the factors for use in assessing the levels and subcellular localization of the factors. iii) isolation of non-DNA binding proteins which interact with DNA-binding factors and iv) studies on regulation of transcription factors during B-cell development. IgH mRNA stability during B-cell development will also be studied. If, as preliminary data suggest, differential mRNa stability is observed, the RNA sequences and cellular proteins which determined this stability will be identified and characterized.